In an image display device that reflects laser light by means of a reflection surface of a deflection means to perform two-dimensional deflection and scanning; and allows an observer to observe an image (virtual image) via an eyepiece optical system, each scanned ray enters the retina, so that observer recognizes the image (so-called Maxwellian view). Accordingly, if the position of the observer's pupil moves around up, down, left and right from the position of an optical pupil formed by the eyepiece optical system, the image ray does not enter the retina, so that it becomes impossible for the observer to observe the image.
Regarding this point, in a patent document 1, for example, in a structure that uses a laser scan optical system, a diffusion plate is disposed in a light path to spread an optical pupil. In this case, even if the position of an observer's pupil moves around up, down, left and right in a plane of the optical pupil, it is possible to guide image rays to the retina, so that the observer is able to observe the image.